1. Field of the Invention
This invention relates to nutrient compositions for mammals and more particularly to nutrient compositions containing oligopeptides and methods of administering them to mammals.
2. Description of the Prior Art
Man and other mammals require protein daily to satisfy vital functions. Proteins are converted to amino acids in the digestive system and the resulting amino acids are employed by the body for growth, development, multiplication and metabolic functions. The human body requires a daily supply of the essential amino acids which are lysine, leucine, isoleucine, tryptophan, methionine, valine, phenylalanine, and threonine. There are other amino acids, called "non-essential," which the body employs as a source of nitrogen. The non-essential amino acids are alanine, glycine, serine, proline, histidine, tyrosine and cysteine.
In the absence of the essential amino acids, there is a rapid deterioration of the nutritional state which results in dysfunction of practically every organ in the body with consequent health problems such as liver failure, anemia, infection, diarrhea and retarded growth.
In the absence of protein or in circumstances where a medical patient is unable to assimilate protein, it is possible to supply free amino acids intravenously and intragastrointestinally as a solution. Elemental diets which were popular in the practice of medicine in the 1970's employed such solutions of free amino acids. These solutions are hypertonic. Hypertonic solutions, whether in the intestines or in the blood vessels are not well tolerated and may cause undesirable effects such as diarrhea and dehydration. These problems may be critical in sick patients.
While the body can matabolize amino acids, the body's transport system can more effectively utilize peptides which can be absorbed and thereafter hydrolyzed within the body's cells to amino acids.
More recent discoveries have indicated that the human digestive system includes separate sites for absorption of dipeptides and absorption of tripeptides in the intestinal mucosa. When absorbed, the dipeptides and tripeptides are hydrolyzed into constituent amino acids. The hydrolysis thus occurs after the peptides are within a body cell. See Adibi and Soleimanpour, J. Clin. Invest. 53: 1368-1374 (1974).
The peptide transport system has the following features:
(a) It does not take up amino acids, but instead transports dipeptides and tripeptides. PA1 (b) It has little or no affinity for peptides with more than three amino acids residues. PA1 (c) It has higher maximum rate of uptake than an amino acid carrier system. PA1 (d) It prefers peptides with lipophilic amino acids in the N-terminal position. PA1 (e) Its greatest activity is in the jejunum and its least activity is in the duodenum with the ileum being between these extremes.
The elemental diets employing free amino acids are usually hypertonic. The hypertonicity creates secondary problems in medical patients with gastrointestinal disorders.
There are reports of the administration of a single dipeptide or a single tripeptide for academic clinical evaluation.
However today there remains a problem of supplying adequate amino acid nutrients to a mammal such as a human medical patient, in a form where the amino acid content can be assimilated by the transport system without the adverse effects of hypertonicity.